A recent news report announces the completion of India’s first underwater railway tunnel under the Hooghly River has been completed.
This will be followed by many more such projects across the country. Railways, especially tunnel railways, depend on infrastructure for perfect operation day in and day out. Cables play an important part not only in supplying power for illumination and other purposes but also for signaling and telecom purposes with the accent on reliability, safety and high performance.
Only the highest quality submarine cables will serve the purpose. Not only cables but the jointing system also plays a crucial role in assured performance. It is a given that cables used for railway tunnels must adhere to international specifications such as conductor current ratings according to IEC 92352, BS 6360 for conductors in insulated cables, IEC 2281 for conductor resistance and IEC 332 part 1&2 for flame retardant properties. Cable design must also conform to MIL DTL 24640B as regards longitudinal water block integrity. There are other parameters to consider such as EM immunity and resistance to stress.
Safety is the prime concern in rail operations and it becomes even more important when trains run in tunnels under water. Cables, whether for power supply or for RF or signaling purposes or even optical fiber cable, must match exceptionally high international standards and be designed as well as manufactured for worst case scenarios.
Different cables are needed for different applications for underwater tunnel railways. For instance, HV and MV feeder cables are used to supply power from substations. Typical cables may include EPR or silicone insulation. In some cases XLPE insulation may be used for high water resistance, oil and water resistance and heat as well as stress resistance. At the same time such cables should have flame retardant chemicals mixed with polymers for fire resistance. These go hand in hand with accessories, jointing and termination connectors.
Grounding and earthing cables are also used for low voltage grounding and for protection against lightning strikes. Then there are halogen-free, low smoke and high fire resistance safety cables typically used for powering lights, ventilation and other emergency equipment. It is usual for such cables to have armored sheathing in addition to special compounded polymer sheaths. Railways also find use for multi-core cables for signaling and telecom purposes.
In the latter case railways also make use of multi-quad cables with multi-pair signaling and twisted pairs for two way low frequency communications. Axle counter cables are also needed to connect trackside counting points and determine a train’s presence and direction of travel, length and number of wagons and their integrity. If high frequency communication equipments are put in place then balise cables with excellent EMC capabilities for radio based GSM-R traffic management. Another type of cable employed by railways is the duo track cables clamped to the tracks for providing routing information.
Polycab, India’s premier cable manufacturer, offers a host of cables for virtually all specific applications as related to railways underwater tunnel projects and assures faultless, reliable performance for years.